To clarify the “trick” above – the image/gopher is gray with a transparent background (that’s a nice thing about SVG, you can do transparent backgrounds).
I put the static image on top of the LED gadget, that’s tied to a on/off tag. I configured that LED to have the same gray color as the image, and black otherwise. So, when the LED is the same color as the image on top of it, you can’t see the image. Otherwise, the background contrasts and TA-DA! You can see the image.
Hope that makes sense!